When do I need to adjust the grind? – The key to perfect coffee extraction
The grind size is one of the most crucial factors for the quality of your coffee. Whether you're using an espresso machine , an AeroPress , a pour-over dripper , or a French press – the grind size determines how quickly water flows through the coffee grounds and how much aroma is extracted.
Especially with espresso, which is extracted under high pressure, even the slightest deviations in grind size can result in a noticeable difference in taste. But when exactly do you need to adjust the grind size – and why?
What you can expect in this post:
- Why the grind size is crucial
- Example: The portafilter – here you can see the difference immediately.
- These factors influence the grind size (regardless of preparation method)
- Typical signs that your grind size is incorrect
- Conclusion: Precision pays off – every gram counts.
1. Why the grind size is crucial
The grind size is the key factor when it comes to extracting flavor compounds from coffee beans . It largely determines how quickly and intensely water comes into contact with the ground coffee – and therefore how much flavor you ultimately get in your cup.
Extraction: Understanding the basics
During brewing, water is forced through the coffee grounds (e.g., with an espresso machine) or flows through them (e.g., with filter coffee). This process extracts soluble components – fats, oils, acids, sugars, bitter substances , and various flavor compounds. However, these substances do not dissolve all at once .
This is where the diagram you uploaded comes into play – the classic extraction curve :
-
Early phase: Acids, fruit components, sweeter notes
-
Middle phase: Body, balance, main aromas
-
Late phase: bitter substances, astringency, ash
If the extraction is too short (because the grind is too coarse ), the brewing process ends before the middle and later aromas develop – the result: sour, thin, underextracted coffee .
If the extraction is too long (because the grind is too fine ), the unwanted bitter substances and tannins are also extracted – the result: bitter, flat, over-extracted coffee .
Grind size = control of the extraction rate
A finer grind increases the surface area of the coffee grounds and slows down the water flow – the water has longer contact time and extracts more components.
A coarser grind reduces the contact time, as the water passes through faster – often too fast to achieve an aromatic balance.
The trick is to hit the sweet spot exactly:
-
Extraction rates between 18% and 22% are considered optimal.
- Below that = underextracted → acidic, empty
- Over-extracted → bitter, woody
Other factors that interact with the grind size
-
Brewing time: Indirectly controlled by the grind size
-
Brewing pressure: Particularly relevant with portafilter machines; excessively fine grinds block pressure build-up.
-
Temperature: Higher temperatures dissolve faster → finer grind = lower temperature if necessary.
-
TDS and EY (Total Dissolved Solids & Extraction Yield): Lab values that show how strongly you are extracting.
Sensory practice: What do you taste?
|
Grind size
|
extraction
|
The taste
|
|
Too delicate
|
Overextraction
|
Bitter, flat, ashy
|
|
Optimal
|
Balanced
|
Sweet, complex, harmonious
|
|
Too rough
|
Underextraction
|
Sour, thin, empty
|
Grind size isn't a rough adjustment – it's a precise, highly sensitive tool. Even the smallest changes affect extraction – especially with espresso, where seconds and micrometers matter. If you want to improve the flavor of your coffee, start with the grind size – it's the key to controlled aroma release .
Example 2: Portafilter: Precision is evident here.
There is hardly any room for error when using a portafilter for espresso:
- The pressure (approx. 9 bar)
- The extraction time (25–30 seconds)
- The flow rate (approx. 25 ml for a single shot)
– they all depend directly on the grind size.
Even a small change – half a dial on the grinder – can significantly affect the taste. Therefore, adjusting the grind setting when using an espresso machine is not only recommended, but essential.
3. Factors that influence the grind size – regardless of the preparation method
Even if you use the same machine, pressure, and temperature, there are many coffee-related variables that will force you to adjust your grind:
degree of roast
The darker the roast , the more porous the bean – it decomposes more easily and becomes “dustier” when ground.
→ Dark roasts often require a slightly coarser grind , as they tend to over-extract quickly with a finer grind.
Light roasts are denser and usually require a finer grind to release enough aromas.
bean size
Beans with a larger diameter (e.g., Maragogype or some varieties from South America) behave differently when ground than smaller beans.
→ Larger beans often require a slightly coarser grind , as their structure slows down the grinding process.
Origin of the beans
Depending on the region of origin , moisture content, density, processing (washed, natural, honey) and storage differ.
→ An Ethiopian natural coffee usually requires a different grind than a Colombian fully washed coffee.
variety
The variety (e.g. Bourbon, Typica, Gesha) influences not only the taste but also the physical structure of the bean.
→ Dense beans like Gesha or Pacamara often require a finer grind .
Blend vs Single Origin
Blends consist of different beans, often with different roast levels and origins.
→ With blends , the grinding process can be uneven – a compromise in grind size is necessary.
→ Single origins can be tuned more precisely, but require regular adjustment in case of temperature or humidity changes.
4. Typical signs that you need to adjust the grind size
Pay attention to these clues in your cup or during the brewing process:
|
symptom
|
Caused
|
measure
|
|
Espresso runs through too quickly
|
Grind too coarse
|
Grind finer
|
|
Bitter taste, too long a run-on time
|
Grind too fine
|
Grind a little coarser
|
|
Little or no crema
|
Underextraction or incorrect pressure
|
Check the grind size, possibly finer.
|
|
Uneven extraction (channeling)
|
Ground material too uneven
|
Grind fresh, clean the mill
|
Conclusion: The grind size is not a detail – it is the basis for taste.
Anyone who is serious about coffee quality cannot ignore the grind size. It is not simply a technical setting on the grinder – it is the central control instrument for extraction , and therefore the decisive factor for taste, balance and clarity in the cup.
Whether in a professional barista setup or an ambitious home barista kitchen: the correct grind balances the aromas. It ensures that fruit acids, sweetness, and body harmonize – and that neither too early nor too late extracted bitter substances disrupt the sensory profile.
Why you need to check the grind setting regularly
The grind size is not a static value. It's a dynamic parameter that can change depending on the bean, batch, roast level, humidity, and even the time of day. Anyone working with high-quality beans—whether single origin or blend , light or dark roast—will quickly realize that each combination requires its own specific adjustment.
External factors such as temperature fluctuations, wear and tear on the grinder, or a change in the coffee bag also affect the grinder and thus the result in the cup. Set it once and forget about it? Doesn't work – not if you want quality.
Good taste begins at the mill.
Investing in a grinder and developing a refined sense of taste is worthwhile. An expensive espresso machine is useless if the grind isn't precisely matched to the bean. Conversely, a simple brewing method, combined with the right grind, can produce surprisingly complex aromas.
He who masters his grinder, masters his coffee.
Takeaways to go
-
The grind size determines the extraction – and therefore your taste.
-
A grind that is too fine makes the coffee bitter, while one that is too coarse makes it taste sour.
-
Each bean (roasting, origin, size, variety) requires its own specific approach.
-
The portafilter shows grind size errors most clearly – use it for calibration.
-
Regular readjustment is not an extra effort, but rather part of quality control.
Coffee is a craft – and the grind is your most important tool. Those who work sensitively, attentively, and precisely will be rewarded with complex, clear, and balanced cups. You don't need a laboratory – you need attention, curiosity, and the willingness to constantly readjust. Because good coffee isn't a matter of chance – it's the result of conscious decisions.
When you should adjust the grind of your coffee
When do I need to adjust the grind? – The key to perfect coffee extraction
The grind size is one of the most crucial factors for the quality of your coffee. Whether you're using an espresso machine , an AeroPress , a pour-over dripper , or a French press – the grind size determines how quickly water flows through the coffee grounds and how much aroma is extracted.
Especially with espresso, which is extracted under high pressure, even the slightest deviations in grind size can result in a noticeable difference in taste. But when exactly do you need to adjust the grind size – and why?
What you can expect in this post:
1. Why the grind size is crucial
The grind size is the key factor when it comes to extracting flavor compounds from coffee beans . It largely determines how quickly and intensely water comes into contact with the ground coffee – and therefore how much flavor you ultimately get in your cup.
Extraction: Understanding the basics
During brewing, water is forced through the coffee grounds (e.g., with an espresso machine) or flows through them (e.g., with filter coffee). This process extracts soluble components – fats, oils, acids, sugars, bitter substances , and various flavor compounds. However, these substances do not dissolve all at once .
This is where the diagram you uploaded comes into play – the classic extraction curve :
If the extraction is too short (because the grind is too coarse ), the brewing process ends before the middle and later aromas develop – the result: sour, thin, underextracted coffee .
If the extraction is too long (because the grind is too fine ), the unwanted bitter substances and tannins are also extracted – the result: bitter, flat, over-extracted coffee .
Grind size = control of the extraction rate
A finer grind increases the surface area of the coffee grounds and slows down the water flow – the water has longer contact time and extracts more components.
A coarser grind reduces the contact time, as the water passes through faster – often too fast to achieve an aromatic balance.
The trick is to hit the sweet spot exactly:
Other factors that interact with the grind size
Sensory practice: What do you taste?
Grind size
extraction
The taste
Too delicate
Overextraction
Bitter, flat, ashy
Optimal
Balanced
Sweet, complex, harmonious
Too rough
Underextraction
Sour, thin, empty
Grind size isn't a rough adjustment – it's a precise, highly sensitive tool. Even the smallest changes affect extraction – especially with espresso, where seconds and micrometers matter. If you want to improve the flavor of your coffee, start with the grind size – it's the key to controlled aroma release .
Example 2: Portafilter: Precision is evident here.
There is hardly any room for error when using a portafilter for espresso:
– they all depend directly on the grind size.
Even a small change – half a dial on the grinder – can significantly affect the taste. Therefore, adjusting the grind setting when using an espresso machine is not only recommended, but essential.
3. Factors that influence the grind size – regardless of the preparation method
Even if you use the same machine, pressure, and temperature, there are many coffee-related variables that will force you to adjust your grind:
degree of roast
The darker the roast , the more porous the bean – it decomposes more easily and becomes “dustier” when ground.
→ Dark roasts often require a slightly coarser grind , as they tend to over-extract quickly with a finer grind.
Light roasts are denser and usually require a finer grind to release enough aromas.
bean size
Beans with a larger diameter (e.g., Maragogype or some varieties from South America) behave differently when ground than smaller beans.
→ Larger beans often require a slightly coarser grind , as their structure slows down the grinding process.
Origin of the beans
Depending on the region of origin , moisture content, density, processing (washed, natural, honey) and storage differ.
→ An Ethiopian natural coffee usually requires a different grind than a Colombian fully washed coffee.
variety
The variety (e.g. Bourbon, Typica, Gesha) influences not only the taste but also the physical structure of the bean.
→ Dense beans like Gesha or Pacamara often require a finer grind .
Blend vs Single Origin
Blends consist of different beans, often with different roast levels and origins.
→ With blends , the grinding process can be uneven – a compromise in grind size is necessary.
→ Single origins can be tuned more precisely, but require regular adjustment in case of temperature or humidity changes.
4. Typical signs that you need to adjust the grind size
Pay attention to these clues in your cup or during the brewing process:
symptom
Caused
measure
Espresso runs through too quickly
Grind too coarse
Grind finer
Bitter taste, too long a run-on time
Grind too fine
Grind a little coarser
Little or no crema
Underextraction or incorrect pressure
Check the grind size, possibly finer.
Uneven extraction (channeling)
Ground material too uneven
Grind fresh, clean the mill
Conclusion: The grind size is not a detail – it is the basis for taste.
Anyone who is serious about coffee quality cannot ignore the grind size. It is not simply a technical setting on the grinder – it is the central control instrument for extraction , and therefore the decisive factor for taste, balance and clarity in the cup.
Whether in a professional barista setup or an ambitious home barista kitchen: the correct grind balances the aromas. It ensures that fruit acids, sweetness, and body harmonize – and that neither too early nor too late extracted bitter substances disrupt the sensory profile.
Why you need to check the grind setting regularly
The grind size is not a static value. It's a dynamic parameter that can change depending on the bean, batch, roast level, humidity, and even the time of day. Anyone working with high-quality beans—whether single origin or blend , light or dark roast—will quickly realize that each combination requires its own specific adjustment.
External factors such as temperature fluctuations, wear and tear on the grinder, or a change in the coffee bag also affect the grinder and thus the result in the cup. Set it once and forget about it? Doesn't work – not if you want quality.
Good taste begins at the mill.
Investing in a grinder and developing a refined sense of taste is worthwhile. An expensive espresso machine is useless if the grind isn't precisely matched to the bean. Conversely, a simple brewing method, combined with the right grind, can produce surprisingly complex aromas.
He who masters his grinder, masters his coffee.
Takeaways to go
Coffee is a craft – and the grind is your most important tool. Those who work sensitively, attentively, and precisely will be rewarded with complex, clear, and balanced cups. You don't need a laboratory – you need attention, curiosity, and the willingness to constantly readjust. Because good coffee isn't a matter of chance – it's the result of conscious decisions.